The End of the World - A Novel by Haruki Murakami

In March of 95, around 6 million people use the Tokyo subway system daily. Dr. Aikao Hayashi is a brilliant heart surgeon with an impressive medical background. He's part of a five man team, which includes three physicists and an electrical engineer. They've left several leaders of liquid sarin in separate cars on three separate subway lines. Just a pinhead sized drop of sarin is enough to kill a healthy human being.